Transcription stops when RNA polymerase reaches a section of DNA called the terminator. Terminatior sequence= AAuAA

Next, the RNA strand is released and RNa polymerase dissociates from the DNA. The RNA strand will go through more processing.

Translation

Forming a polypeptide. Uses mRNA as a template for a.a sequence

Three TRNA Binding sites

1. A site= holds tRNA that is carrying the next amino acid to be added

2. P site= holds tRNA that is carrying the growing polypeptede chain.

3. E site= where discharged tRNAs leave the ribosome

Translation

mRNA-> Ribosome

Uses tRNA to interpreter of mRNA

Large and Small subunit of ribosomes

each has three binding sites for tRNA on its surface. Each has one binding site for mRNA. Facilitates codon and anticodon bonding.

Initiation Step 1

Brings together mRNA, tRNA and ribosomal subunits

Initiation Step 2

Small ribosomal subunits binds tomRNA and initiator tRNA

-Start codon= Aug

-Start anticodon=Uac

-Small ribosomal subunit attaches to 5prime end of mRNA

-downstream from the 5 prime end is start codon AUG (mRNA)

-After the union of mRNA, tRNA and small subunit, the large ribosomal subnit attaches.

What is needed for initiation of RNA?

tRNA mRNA small and Large subunit

Translation of RNA

Amino acids are added one by one to the first amino acid. Step one Codon recognition, mRNA codon in the A site forms hydrogen bonds with the tRNA anitcodon. Step 2- Peptide bond formation, The polypeptide extending from the P site moves A site to attach to the new a.a.

RNA Translocation

The tRNA w/ the polypeptide chain in the A site translocated to the P site. tRNA at the P site moves to the E site and leaves the ribosome.

RNA Termination

Happens at the stop codon (Uaa, Uag, and Uga) The polypeptides is freed from the ribosome and the reso of the translation assembly comes apart.

Differences in gene expression between the two main types of cells

Prokaryotes= genes are a continuous streach of DNA

Eukaryotes= genes are fragmented. fragments are made of exons that are interrupted frequent by non-coding regions called introns.